Backup control for hvac system

ABSTRACT

An equipment interface module that can operate one or more pieces of HVAC equipment in accordance with instructions received from a properly operating thermostat, yet can also operate the HVAC equipment when communications between the thermostat and the HVAC controller are lost due to, for example, low battery power at the thermostat, malfunctioning thermostat sensor(s), malfunctioning communication and/or thermostat circuitry, electrical interference, and the like. In some instances, the equipment interface module may regulate the HVAC equipment in accordance with a signal from a remote sensor when communication with the thermostat is lost.

TECHNICAL FIELD

The disclosure relates generally to HVAC systems, and more particularlyto HVAC systems that employ remotely located thermostats.

BACKGROUND

Many residential and commercial buildings include one or more remotelylocated thermostats for controlling the HVAC equipment used to heat,cool, control humidity, and/or ventilate the building. The thermostattypically monitors air temperature and/or other parameters within thebuilding, and provides appropriate instructions to the HVAC equipment inorder to control selected environmental parameters such as temperatureand/or humidity within the building space.

Some thermostats are powered by electrical lines that extend between thethermostat and the HVAC equipment. Other thermostats rely on one or morebatteries disposed within the thermostat to power the thermostat. Somethermostats have wired connections to the HVAC equipment, while otherscommunicate with the HVAC equipment over a wireless connection.

It will be appreciated that when a thermostat loses power (e.g. via abattery failure) and/or loses communication with HVAC equipment (e.g.via battery failure and/or wireless connection failure), the thermostatwill cease to provide the desired instructions to the HVAC equipment.This may cause conditions within the building to fall outside of desiredenvironmental parameter levels. For example, if during a hot day, thethermostat ceases to provide the desired instructions to the HVACequipment, the building interior may become excessively hot and/orhumid. This may be problematic, particularly for people having increasedsensitivity to heat. Also, excessive humidity, which if allowed topersist for a sufficient period of time, can cause mold and/or otherdamage to the building. Similarly, if during a cold day, the thermostatceases to provide the desired instructions to the HVAC equipment, thebuilding interior may become excessively cold, which under somecircumstances, may cause pipes to freeze and/or cause other damage tothe building.

A need exists, therefore, for an HVAC controller that can operate one ormore pieces of HVAC equipment in accordance with instructions receivedfrom a properly operating thermostat, yet can also operate the HVACequipment when communications between the thermostat and the HVACcontroller are lost due to, for example, low battery power at thethermostat, malfunctioning thermostat sensor(s), malfunctioningcommunication and/or thermostat circuitry, electrical interference, andthe like.

SUMMARY

The disclosure pertains generally to an HVAC controller that can operateone or more pieces of HVAC equipment in accordance with instructionsreceived from a properly operating thermostat, yet can also operate theHVAC equipment when communications between the thermostat and the HVACcontroller are lost due to, for example, low battery power at thethermostat, malfunctioning thermostat sensor(s), malfunctioningcommunication and/or thermostat circuitry, electrical interference, andthe like.

An illustrative but non-limiting example of may be found in an HVACsystem that includes an HVAC component having an HVAC controller, aremotely located wireless thermostat, and an equipment interface modulethat is in communication with the wireless thermostat. In some cases,the equipment interface module may be configured to provide instructionsto the HVAC component in accordance with and/or in response toinstructions received from a properly operating thermostat. Theequipment interface module may also be configured to provideinstructions to the HVAC component if/when the equipment interfacemodule loses communication with the wireless thermostat.

Another illustrative but non-limiting example of the disclosure may befound in a method of operating an HVAC system that includes an HVACcomponent and an HVAC controller, a wireless thermostat, an equipmentinterface module disposed exterior to the HVAC component, and a remotesensor. The HVAC component may be operated in accordance withinstructions received from the wireless thermostat. If communicationbetween the wireless thermostat and the equipment interface modulefails, the HVAC component may be controlled via the equipment interfacemodule and the remote sensor until communication is restored.

Another illustrative but non-limiting example of the disclosure may befound in an equipment interface module that is configured to communicatewith a wireless thermostat and a remote sensor and is configured tocontrol an HVAC component that includes a circulating blower. In somecases, the equipment interface module may include an RF transceiver anda controller. The controller may be configured to recognize if/whencommunication between the wireless thermostat and the equipmentinterface module is lost, start the circulating blower whencommunication is lost, and operate the HVAC component in accordance witha signal from the remote sensor until communication between the wirelessthermostat and the equipment interface module is restored. In somecases, the remote sensor may be positioned in fluid communication withthe return air duct of the building, but this is not required.

The preceding summary is provided to facilitate an understanding of someof the features unique to the present invention and is not intended tobe a full description. A full appreciation of the invention can begained by taking the entire specification, claims, drawings, andabstract as a whole.

BRIEF DESCRIPTION

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments in connection withthe accompanying drawings, in which:

FIG. 1 is an illustrative but non-limiting example of an HVAC systemthat employs a remotely located thermostat;

FIG. 2 is an illustrative but non-limiting example of an equipmentinterface module that may be used within the HVAC system of FIG. 1; and

FIGS. 3-4 are flow diagrams showing some illustrative but non-limitingexamples of methods that may be carried out using the HVAC system ofFIG. 1.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

The following description should be read with reference to the drawings,in which like elements in different drawings are numbered in likefashion. The drawings, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of theinvention. Although examples of construction, dimensions, and materialsare illustrated for the various elements, those skilled in the art willrecognize that many of the examples provided have suitable alternativesthat may be utilized.

FIG. 1 is a schematic illustration of an HVAC system 10 that includes anHVAC component 12. HVAC component 12 may, for example, be a forced airfurnace and/or an air conditioning unit, although any suitable HVACcomponent may be used. In some instances, HVAC component 12 may includea circulating air blower 14 that pulls return air into HVAC component 12via a return air duct 16 and subsequently blows conditioned air backinto the building via a conditioned air duct 18.

While not illustrated, it will be appreciated that HVAC component 12 mayinclude a heating apparatus that includes a burner, a gas valveproviding fuel to the burner, a heat exchanger and a collector box. Acombustion blower may pull combustion air through the heating apparatusand exhaust the combustion gases through an exhaust flue. Alternatively,or in addition, HVAC component 12 may include an air conditioning coil.Circulating air blower 14 may blow return air across the airconditioning coil in order to cool and dry the air before the airreturns to the house via conditioned air duct 18. It should berecognized that these are only illustrative HVAC components.

In some instances, HVAC component 12 may include an HVAC componentcontroller 20. HVAC component controller 20 may, in some instances,control one or more HVAC components. For example, HVAC componentcontroller 20 may be an integrated furnace controller that is configuredto control various components of HVAC system 10, such as the ignition offuel by an ignition element (not shown), the speed and operation timesof the aforementioned combustion blower, the speed and operation timesof circulating air blower 14 and/or the activation and deactivation ofan air conditioner coil. Alternatively, or in addition, HVAC componentcontroller 20 can be configured to monitor and/or control various otheraspects of the HVAC system 10 including any damper and/or divertervalves connected to the supply air ducts, any sensors used for detectingtemperature and/or airflow, any sensors used for detecting filtercapacity, and any shut-off valves used for shutting off the supply ofgas to the gas valve. This is only illustrative.

In some cases, HVAC component controller 20 may be configured to receiveelectrical signals from one or more remotely located thermostats thatmonitor temperature and perhaps other HVAC system parameters such ashumidity within a building. However, in some instances, HVAC componentcontroller 20 may instead be electrically connected to, or integralwith, a controller such as an equipment interface module 22. While twoelectrical lines 24, 26 are shown, it will be appreciated that this isonly illustrative of a communications path. In some cases, there may bemore or less than two electrical lines connecting HVAC componentcontroller 20 and equipment interface module 22. In some cases, it iscontemplated that equipment interface module 22 may communicatewirelessly with HVAC component controller 20.

Equipment interface module 22 may communicate with a thermostat 28, asshown. In some cases, thermostat 28 may be hard-wired to equipmentinterface module 22 via an electrical connection 30. In some instances,the thermostat 28 may be battery powered, and may not draw any powerfrom the electrical connection 30, either parasitically or via adedicated power line, from HVAC component 12. In such instances, theelectrical connection 30 may be used by the thermostat 28 to sendinstructions to the equipment interface module 22.

In some case, thermostat 28 may be a wireless thermostat that isconfigured to communicate wirelessly with equipment interface module 22.When so provided, the thermostat may be solely battery powered, or mayreceive power from electrical connection 30, as desired. In either case,equipment interface module 22 may include a wireless communicationssystem 32 as well as a controller 34. In some cases, wirelesscommunications system 32 may be an RF (radio frequency) wirelesscommunications system, but it is contemplated that any suitable wirelesscommunication path may be used, as desired. In some instances, theequipment interface module 22 may include an RF receiver and thewireless thermostat may include an RF transmitter. One or two-waycommunication may be provided, as desired.

Controller 34 may be configured to provide appropriate instructions toHVAC component controller 20 in response to calls for heating and/orcooling that may originate from thermostat 28. While not expresslyillustrated, controller 34 may include memory that may be used to storeprogramming as well as a processor that may carry out the programminginstructions.

It will be appreciated that in some instances, communication betweenequipment interface module 22 and thermostat 28 may be interrupted forany number of reasons. For example, communication between equipmentinterface module 22 and thermostat 28 may be interrupted because of lowbattery power at the thermostat 28, malfunctioning thermostat sensor(s),malfunctioning communication and/or thermostat circuitry, electricalinterference, and the like.

In some cases, equipment interface module 22 may be programmed tooperate HVAC component 12 in the absence of any communication betweenequipment interface module 22 and thermostat 28. In some instances, HVACsystem 10 may include one or more remote sensors that can, if desired,provide appropriate signals to equipment interface module 22 so thatequipment interface module 22 can reasonably regulate air temperatureand/or other parameters such as humidity within a building. That is,equipment interface module 22 may provide backup control to the HVACsystem 10 when communication between the equipment interface module 22and the thermostat 28 is interrupted for any number of reasons.

In some instances, HVAC system 10 may include a return air sensor 36that can be configured to provide equipment interface module 22, viaelectrical (or wireless) connection 38, with information pertaining toenvironmental conditions within the building. Return air sensor 36 maybe a temperature sensor and/or a humidity sensor. In some cases,equipment interface module 22 may be configured to accept other remotetemperature signals. For example, HVAC system 10 may include a remotetemperature sensor 40 that can be a temperature sensor that is locatedsomewhere in the building and that can provide a signal to equipmentinterface module 22 via a wired or wireless connection 42. In somecases, remote temperature sensor 40 may be an outdoor air temperaturesensor.

In some cases, remote temperature sensor 40 may represent a temperaturesensor disposed within a remote control for thermostat 28. In somecases, particularly if HVAC system 10 is located within a zoned buildinghaving two or more thermostats (not illustrated), it is contemplatedthat remote temperature sensor 40 may represent a working thermostatthat can provide a temperature signal to equipment interface module 22when one or more of the other thermostats within the system have stoppedworking or at least have stopped communicating with equipment interfacemodule 22.

As noted above, equipment interface module 22 may, in response to callsfor heat and/or cooling from thermostat 28, provide appropriateinstructions to HVAC component controller 20. Equipment interface module22 may be programmed to check for a signal from thermostat 28. Ifequipment interface module 22 does not receive a signal from thermostat28, over a predetermined length of time, equipment interface module 22may determine that communication between equipment interface module 22and thermostat 28 has been at least temporarily lost. In some cases,equipment interface module 22 may be configured to ping thermostat 28 inaccordance with a particular schedule, or perhaps only when no signalshave been received by equipment interface module 22.

In any event, once equipment interface module 22 has determined thatcommunication has at least temporally been lost, equipment interfacemodule 22 may step in and provide appropriate instructions to HVACcomponent controller 20, even without input from thermostat 28. In anillustrative but non-limiting example, equipment interface module 22 mayoperate HVAC component 12 in accordance with a sensor signal from returnair sensor 36 and/or remote temperature sensor 40. In some cases,particularly if equipment interface module 22 is relying on a signalfrom return air sensor 36, equipment interface module 22 may instructHVAC component controller 20 to operate circulating air blower 14continuously for a period of time to move house air past return airsensor 36 so that a more representative temperature (or other parameter)may be obtained.

In some instances, equipment interface module 22 may provide signals forheating or cooling to HVAC component controller 20 in order to maintainbuilding air temperature (as indicated by return air sensor 36) at apredetermined set point. In some instances, equipment interface module22 may maintain building air temperature in accordance with the mostrecent temperature set point used by thermostat 28. In some cases,equipment interface module 22 may maintain the building air temperatureat a level that is safe, but is sufficiently moved from a previous setpoint so that the building occupants may sense that something is notcorrect, and may check thermostat 28. In some instances, equipmentinterface module 22 may maintain the building air temperature at a setpoint of 65° F. for heating and 80° F. for cooling, but this isillustrative only. In some cases, the equipment interface module 22 maycontrol the building air temperature in accordance with a schedule, suchas an Energy Star™ schedule. Alternatively, or in addition, humidityand/or other parameters may be similarly controlled by the equipmentinterface module 22, if desired.

If thermostat 28 is completely without power, it may appear dead to theuser, indicating to the user that the battery may have failed. In somecases, if thermostat 28 is too low on power to provide a wireless signalto equipment interface module 22 yet retains some power, a LOW BATTERYor similar indication may be indicated by thermostat 28. If thethermostat 28 has sufficient power, but the wireless communication linkhas failed, the thermostat itself may provide an indication to the userthat the wireless communication link has failed. In some instances,equipment interface module 22 may itself provide a visual indicationthat communication has failed.

In some cases, equipment interface module 22 may retain equipmentconfiguration information that may have previously been provided bythermostat 28 or perhaps is indicated by one or more settings made by aninstaller. For example, HVAC component 12 may include a single stagefurnace, a two stage furnace, a modulating furnace, a single stage airconditioning unit, a two stage air conditioning unit, a one, two orthree stage heat pump, and the like. Similarly, thermostat 28 may be asingle stage thermostat or a two-stage thermostat. Equipment interfacemodule 22 may store this information in a non-volatile memory, and thenprovide the appropriate instructions to properly operate HVAC component12 via a sometimes simplified control algorithm.

In one example, if HVAC component 12 has more than one heating stage,equipment interface module 22 may track how fast the building airtemperature (as indicated by remote air sensor 36) is changing inresponse to equipment interface module 22 turning on first stage heat.If the temperature is changing too slowly, equipment interface module 22may instruct HVAC component controller 20 to activate second stage heat.Once the building temperature approaches the desired temperature,equipment interface module 22 may first stop second stage heat and thensubsequently stop first stage heat once the desired temperature has beenachieved. In some instances, equipment interface module 22 may insteadactivate first stage heat, second stage heat and/or even an additionalheat stage, auxiliary heat or emergency heat based upon a temperaturedifference between a set point and a temperature detected by return airsensor 36.

FIG. 2 is a schematic front view of an illustrative equipment interfacemodule 22. The illustrative equipment interface module 22 has a housing44. It will be appreciated that housing 44 may be configured toaccommodate appropriate wiring connections between equipment interfacemodule 22 and HVAC component controller 20 (FIG. 1), such as electricalconnections 24 and 26 (FIG. 1). Appropriate wiring connections may bemade along a side or a rear surface of housing 44. In some cases, aportion of the front of housing 44 may be hinged to provide necessaryaccess to a wiring block. This is just one illustrative embodiment. Insome instances, the equipment interface module 22 may be integrated withthe HVAC component controller 20, but this is not required.

In an illustrative but non-limiting example, equipment interface module22 may include a system status board 46 that may include one or moreLEDs (light emitting diodes) that can light to show system status.Examples of lights that may be included within system status board 46include a POWER light 48, a HEAT light 50, a COOL light 52 and/or a FANlight 54 that may light as appropriate to show current system status. Itis contemplated that additional system status lights may be included, asdesired and/or appropriate given the particulars of HVAC system 10 (FIG.1).

Equipment interface module 22 may, in some cases, include a wirelessstatus board 56. Wireless status board 56 may include a connectionbutton 58 that may be used to establish wireless communication with athermostat 28 (FIG. 1) and/or any other wireless devices within HVACsystem 10. Wireless status board 56 may include a wireless status light60 that provides an indication of current communications status. Forexample, wireless status light 60 may be an LED that glows green whencommunication is established, and glows red when communication hasfailed. In some instances, wireless status light 60 may blink greenwhile in the process of attempting to establish wireless communicationwith thermostat 28 and/or another wireless device, but this is notrequired.

FIG. 3 is a flow diagram showing an illustrative but non-limitingexample of a method that may be carried out via HVAC system 10 (FIG. 1).Control begins at block 62, where an HVAC component such as HVACcomponent 12 (FIG. 1) is operated in accordance with instructionsreceived from a wireless thermostat such as thermostat 28 (FIG. 1). At64, equipment interface 22 (FIG. 1) detects if communication between thewireless thermostat and the equipment interface module 22 has failed.

If communication has failed, control passes to block 66 where HVACcomponent 12 (FIG. 1) is controlled via equipment interface module 22and a remote sensor such as a return air sensor 36 (FIG. 1) and/orremote temperature sensor 40 (FIG. 1) until communication betweenequipment interface module 22 and the wireless thermostat isreestablished. In some instances, the remote sensor is used to detect asystem parameter such a temperature and/or humidity, and HVAC component12 is operated to maintain a predetermined value for the systemparameter.

FIG. 4 is a flow diagram showing an illustrative but non-limitingexample of a method that may be carried out via HVAC system 10 (FIG. 1).Control begins at block 62, where an HVAC component such as HVACcomponent 12 (FIG. 1) is operated in accordance with instructionsreceived from a wireless thermostat such as thermostat 28 (FIG. 1). At64, equipment interface 22 (FIG. 1) detects if communication between thewireless thermostat and the equipment interface module 22 has failed.

If communication has failed, control passes to block 68, where a systemparameter such as air temperature (and/or humidity) is detected via aremote sensor such as remote air sensor 36 (FIG. 1). As seen at block70, the circulating air blower 14 (FIG. 1) may be then be operatedcontinuously so that remote air sensor 36 provides a more accuraterepresentation of conditions within the building. Equipment interfacemodule 22 monitors the return air temperature as seen at block 72, andthen controls HVAC component 12 (FIG. 1) to attain and then maintain adesired return air temperature.

The invention should not be considered limited to the particularexamples described above, but rather should be understood to cover allaspects of the invention as set out in the attached claims. Variousmodifications, equivalent processes, as well as numerous structures towhich the invention can be applicable will be readily apparent to thoseof skill in the art upon review of the instant specification.

1. An HVAC system comprising: an HVAC component having an HVACcontroller; a remotely located wireless thermostat; and an equipmentinterface module in communication with the wireless thermostat, theequipment interface module configured to provide instructions to theHVAC controller in response to signals received from the wirelessthermostat; wherein the equipment interface module is also configured toprovide instructions to the HVAC controller without input from thethermostat if/when the equipment interface module loses communicationwith the wireless thermostat.
 2. The HVAC system of claim 1, furthercomprising a remote sensor that is in communication with the equipmentinterface module, the remote sensor providing the equipment interfacemodule with a control signal related to an environmental parameterwithin a building.
 3. The HVAC system of claim 2, wherein the HVACcomponent comprises a forced air HVAC unit having a circulating blower,and the equipment interface module is configured to activate thecirculating blower in order to move air past the remote sensor when theequipment interface module loses communication with the wirelessthermostat.
 4. The HVAC system of claim 3, wherein the equipmentinterface module operates the circulating blower continuously untilcommunication is restored between the equipment interface module and thewireless thermostat.
 5. The HVAC system of claim 1, wherein theequipment interface module operates the HVAC component in accordancewith a predetermined temperature setpoint when communication is lostbetween the equipment interface module and the wireless thermostat. 6.The HVAC system of claim 1, wherein the wireless thermostat comprises abattery, and communication between the equipment interface module andthe wireless thermostat is lost as a result of the battery havinginsufficient energy to operate the wireless thermostat.
 7. The HVACsystem of claim 1, wherein the wireless thermostat comprises an RFtransmitter and the equipment interface module comprises an RF receiver.8. The HVAC system of claim 1, wherein the forced air HVAC unitcomprises a furnace.
 9. The HVAC system of claim 1, wherein the forcedair HVAC unit comprises an air conditioner.
 10. The HVAC system of claim2, wherein the remote sensor comprises a return air temperature sensor.11. The HVAC system of claim 2, wherein the remote sensor comprises atemperature sensor disposed within a thermostat remote control.
 12. TheHVAC system of claim 2, wherein the remote sensor comprises an outdoorair sensor.
 13. The HVAC system of claim 2, wherein the remote sensorcomprises a humidity sensor and the equipment interface module isconfigured to operate the HVAC component to limit a humidity level whencommunication is lost between the equipment interface module and thewireless thermostat.
 14. The HVAC system of claim 1, wherein theequipment interface module is configured to remember equipmentconfiguration information previously provided by the wirelessthermostat.
 15. The HVAC system of claim 14, wherein the equipmentinterface module is configured to provide instructions to the HVACcontroller, in the absence of communication with the wirelessthermostat, in accordance with the remembered equipment configuration.16. A method of operating an HVAC system comprising an HVAC componentand an HVAC controller, a wireless thermostat, a equipment interfacemodule exterior to the HVAC component and a remote sensor, the methodcomprising the steps of: operating the HVAC component in accordance withinstructions received from the wireless thermostat; detecting ifcommunication between the wireless thermostat and the equipmentinterface module fails; and controlling the HVAC component via theequipment interface module and the remote sensor until communicationbetween the wireless thermostat and the equipment interface module isreestablished.
 17. The method of claim 16, wherein controlling the HVACcomponent via the equipment interface module and the remote sensorcomprises detecting an environmental parameter using the remote sensor,and controlling the HVAC component in accordance with a predeterminedvalue of the environmental parameter.
 18. The method of claim 17,wherein the HVAC component comprises a forced air HVAC unit having ablower and the environmental parameter comprises a return airtemperature, and controlling the HVAC component via the equipmentinterface module and the remote sensor comprises: operating the blowercontinuously; monitoring the return air temperature; and controlling theHVAC component to achieve a desired return air temperature.
 19. Anequipment interface module configured to communicate with a wirelessthermostat and a remote sensor, the equipment interface moduleconfigured to provide instructions to an HVAC component including acirculating blower, the equipment interface module comprising: an RFreceiver; and a controller that is configured to recognize if/whencommunication between the wireless thermostat and the equipment moduleis lost; start the circulating blower when communication is lost; andoperate the HVAC component in accordance with a signal from the remotesensor until communication between the wireless thermostat and theequipment module is restored.
 20. The equipment interface module ofclaim 19, wherein the remote sensor comprises a return air temperature,the controller configured to: operate the blower continuously; monitorthe return air temperature; and control the HVAC component to achieve adesired return air temperature.